fix(login): address review feedback on language dropdown PR

- Fix import path: use i18n barrel instead of TranslationContext directly
- Encapsulate localStorage key behind hasStoredLanguage() helper in settingsStore
- Fix pt-BR detection: only map pt-BR to br, pt-PT now returns null correctly
- Add comment linking server SUPPORTED_LANG_CODES to canonical client source
- Extract /api/config inline handler to routes/publicConfig.ts
- Add aria-haspopup, aria-expanded, role=listbox/option, aria-selected to dropdown
- Add 8 tests for detectBrowserLanguage (FE-COMP-I18N-016–023)
- Add 3 tests for setLanguageTransient (FE-STORE-SETTINGS-015–017)

server/src/app.ts

@@ -6,7 +6,7 @@ import path from 'node:path';
 import fs from 'node:fs';
 
 import jwt from 'jsonwebtoken';
-import { JWT_SECRET, DEFAULT_LANGUAGE } from './config';
+import { JWT_SECRET } from './config';
 import { logDebug, logWarn, logError } from './services/auditLog';
 import { enforceGlobalMfaPolicy } from './middleware/mfaPolicy';
 import { authenticate } from './middleware/auth';
@@ -41,6 +41,7 @@ import notificationRoutes from './routes/notifications';
 import shareRoutes from './routes/share';
 import journeyRoutes from './routes/journey';
 import journeyPublicRoutes from './routes/journeyPublic';
+import publicConfigRoutes from './routes/publicConfig';
 import { mcpHandler } from './mcp';
 import { Addon } from './types';
 import { getPhotoProviderConfig } from './services/memories/helpersService';
@@ -194,7 +195,7 @@ export function createApp(): express.Application {
   app.use('/api/trips/:tripId/reservations', reservationsRoutes);
   app.use('/api/trips/:tripId/days/:dayId/notes', dayNotesRoutes);
   app.get('/api/health', (_req: Request, res: Response) => res.json({ status: 'ok' }));
-  app.get('/api/config', (_req: Request, res: Response) => res.json({ defaultLanguage: DEFAULT_LANGUAGE }));
+  app.use('/api/config', publicConfigRoutes);
   app.use('/api', assignmentsRoutes);
   app.use('/api/tags', tagsRoutes);
   app.use('/api/categories', categoriesRoutes);